Comparison Formula error using vba

Hello All,

I am using below vba macro that looks in D column cell values and equates/ copy pastes in Col A those values that are available in Col D but not in A. After using below formula, I however get missing values in Col A but additionally getting 0's in Col A. Please help me to correct this error. OR Is there any way using vba to get desired results. Thank you

Examples of before and after using formulas are shown in figure

Sub fillIntheBlank()
Set WkRg = Worksheets("sheet1").UsedRange
    Set WkRg = Intersect(WkRg, WkRg.Offset(3, 0))
    
    If Application.CountBlank(WkRg.Columns(1)) <> 0 Then
        With WkRg.Columns(1).SpecialCells(xlCellTypeBlanks)
                .Formula = "=RC[3]"
        End With
    End If
End Sub

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